Generation of highly uniform droplets using asymmetric microchannels fabricated on a single crystal silicon plate: Effect of emulsifier and oil types

Abstract

Uniform droplets of soybean oil, MCT (medium-chain fatty acid triglyceride) oil and ntetradecane with a mean diameter of 26-29 m have been generated using a silicon 24  24 mm microchip consisting of 23,489 asymmetric microchannels fabricated by photolitography and deep reactive ion etching. Each microchannel consisted of a circular 10-m diameter straight hole with a length of 70 m and a 50  10 m rectangular microslot with a depth of 30 m. At the constant oil flux of 10 Lm -2 h -1 , the percent of active channels increased with increasing the oil viscosity and ranged from 4 % for n-tetradecane to 48 % for soybean oil. The size distribution span for SDS (sodium sodium dodecyl sulphate)-and Tween 20 (polyoxyethylene (20) sorbitan monolaurate)-stabilised soybean and MCT oil droplets was 0.21-022. The ability of asymmetric microchannels to generate monodisperse soybean oil droplets at the very low SDS concentration of 0.01 wt% has been demonstrated. At the SDS concentration below the CMC, the generated droplets tend to attach to the plate surface, whereas at the higher SDS concentration they detach from the plate as soon as they are formed. The agreement between the experimental and CFD (Computational Fluid Dynamics) simulation results was excellent for soybean oil and the poorest for n-tetradecane.

Structured Biodegradable Polymeric Microparticles for Drug Delivery Produced Using Flow Focusing Glass Microfluidic Devices

“…Microfluidic methods allow production of particles with low polydispersity (CV = Standard Deviation/Mean < 3%) and high encapsulation efficiency that are perfectly tailored to meet the needs of pharmaceutical industry. 30 However, microfluidic droplet generators are typically planar (2-D) and made from single crystal silicon chips using expensive microfabrication methods 31 or mouldable polymers such as polydimethylsiloxane (PDMS), which swell and deform in contact with organic solvents. 29 Here, we investigate formation of structured polymeric microspheres using glass capillary microfluidic devices.…”

Effect of viscosities of dispersed and continuous phases in microchannel oil-in-water emulsification

“…Commonly used and studied microtechnological emulsification devices can be driven by transversal flow (T-and Y-junctions (Garstecki et al 2006;van der Graaf et al 2005;Steegmans et al 2009)), coflow (flow-focusing devices (Anna et al 2003;Xu and Nakajima 2004)) or by interfacial tension (also called spontaneous droplet formation; grooved microchannels (Kawakatsu et al 1997) and straight-through microchannels (Kobayashi et al 2002)). Several researchers explored the influence of system parameters on micro-emulsification processes and observed that droplet size can be varied by the design of the microfluidic device (Van Dijke et al 2008;Sugiura et al 2002;Kobayashi et al 2005), the flow rates of both phases (Garstecki et al 2004), and the properties of the liquids and other ingredients (Saito et al 2005;Vladisavljević et al 2008).…”

Controlled production of oil-in-water emulsions containing unrefined pumpkin seed oil using stirred cell membrane emulsification

“…It may happen if there is a large number of drops at the membrane surface and the drop diameter is bigger than the distance between the pores, so that the drops push each other at the membrane surface [27]. The drops can also be deformed from their spherical shape if they are generated at the pores or channels with a distinct non-spherical shape such as rectangular channels with a high aspect ratio [28] and asymmetric microchannels [29] or if the droplets are squeezed between a microstructured substrate and a cover glass before detachment [30]. However, it is widely accepted that the shear stress at the membrane surface does have to be applied to obtain uniform drops at relatively high drop productivity.…”